Along with the trend of high frequency, miniaturization, and high integration, heat, static electricity, and electromagnetic waves significantly affect electronic devices and information/communication devices. For example, as performances of high frequency electronic devices, e.g., the processing speed of microprocessors and the storage capacity of memories are increased, and the size thereof is decreased, they emit a larger amount of heat and electromagnetic waves. In addition, such high frequency electronic devices or modules are susceptible to heat, static electricity, and electromagnetic waves around them.
Thus, in order to prevent electromagnetic waves from being emitted out of a high frequency electronic device or module, or to shield a high frequency electronic device or module from external electromagnetic waves, the high frequency electronic device or module is covered with an electromagnetic interference (EMI) shield case, and then, the EMI shield case is electrically and mechanically connected to a ground pattern of a printed circuit board.
In this case, the EMI shield case includes an electrical conductive member such as a metal sheet to block electromagnetic waves, and has a box shape with at least one opening to cover an electronic device or module mounted on the printed circuit board.
The EMI shield case has a certain strength to protect an inner electronic device or module from external force or shock. Particularly, small and portable high frequency devices such as mobile phones include a slim and high strength EMI shield case.
For example, an EMI shield case may be adapted for a reflow soldering process through vacuum pickup.
In general, an EMI shield case including a metal sheet is used to protect a high frequency electronic device or module mounted on a printed circuit board from electromagnetic waves. To fabricate such an EMI shield case, a high strength metal sheet formed of stainless steel, for example, SUS 301 with a thickness of about 0.15 mm may be pressed using a press mold. Then, the EMI shield case may be tinned to be directly soldered to a ground pattern, or be fitted in a plurality of metal clips soldered in advance to a ground pattern.
As such, a typical EMI shield case is fabricated by pressing a metal sheet with a press mold. To produce EMI shield cases in small quantities, a metal sheet may be etched and bent using a low-priced mold.
However, such EMI shield cases and fabrication methods thereof are appropriate for mass production. That is, typical EMI shield cases and fabrication methods thereof are inappropriate to fabricate a pilot model or a prototype model. Particularly, the position of a circuit, a ground pattern, and an electronic device on a printed circuit board may be variously designed and be occasionally changed for satisfying appropriate electric and mechanical characteristics, and various design changes for dissipating heat may be made. Thus, when EMI shield cases appropriate to variously and occasionally designed circuits and ground patterns are fabricated using the above described methods, the following limitations may be encountered.
1) When EMI shield cases corresponding to changeable circuits and ground patterns are fabricated in small quantities, a press process using a press mold, or an etching and bending process takes a long time and high cost. As a result, it may be difficult to effectively correspond to quick and various design processes for a circuit and a ground pattern.
2) It takes a long time and high cost to modify a press mold or a bending mold.
3) It takes a long time and high cost to optimize an EMI shield case to suit a certain purpose.
4) A mold design for fabricating an EMI shield case requires specialized skills.
5) It is difficult to reliably solder a small metal clip to a ground pattern of a printed circuit board.